Ultra small carbon pores may store energy

By MIKE MARTIN, UPI Science News   |   March 15, 2002 at 2:56 PM
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COLUMBIA, Mo., March 15 (UPI) -- Nanometer-size pores in carbon may solve a dilemma that has plagued alternative fuel advocates for years -- how to safely store natural gas at low pressures that reduce the risk of explosion.

While studying the internal structure of activated carbon -- a porous material commonly used in air filtration and water purification -- University of Missouri physicist Peter Pfeifer and his collaborators discovered "carbon nanopores," a network of uniform, one to two nanometer channels that penetrate the carbon.

"We believe carbon nanopores have potential for a number of applications, the most promising of which is alternative fuel storage, particularly of methane gas," Pfeifer explained.

Currently, methane is stored in heavy-walled steel cylinders under extreme pressure -- more than 3,000 psi, or pounds per square inch. A cylinder under such pressure used as a vehicular fuel tank would explode in an accident.

Pfeifer told United Press International if carbon nanopores were used, methane could be stored safely.

"Our material offers a number of advantages for methane storage -- it's lightweight, easy to manufacture in large quantities and relatively inexpensive," he said. "But most importantly, it would allow the methane to be stored at a safer, significantly lower pressure -- about 530 psi -- which reduces the risk of an explosion should a methane-powered vehicle be in an accident."

A carbon nanopore gasoline tank "would be filled with the carbon," Pfeifer told UPI. "It would look like your tank was filled with charcoal, pressed into a large cube or so."

The Earth may hold a 10,000-year reserve of cleaner-burning methane gas, Pfeifer said. He believes a commercially viable carbon nanopore storage product could be on the market within five years. Other experts are not as certain.

"I would say that other options, such as converting natural gas to liquid distillates that can be refined and sold as gasoline, would come to market more quickly than this carbon nanopore solution," Michelle Michot Foss, executive director of the Institute for Energy, Law & Enterprise, told United Press International from the University of Houston. "Gas to liquid technology is something everyone is working on right now."

"The conversion of methane gas into liquid distillates is more expensive, does not give the benefit of low pollution, and works only for internal combustion engines," Pfeifer told UPI. "In the long run, methane is of foremost interest for fuel-cell operated cars --electric cars -- in which methane is either the direct fuel for the battery --a methane-based fuel cell -- or else is converted into hydrogen for hydrogen-based fuel cells."

Other potential applications of carbon nanopores include ultra-fine air filters, gas masks, food purification, and electricity storage.

"Super capacitors built from carbon nanopores filled with a conducting fluid could store electricity, for instance," Pfeifer told UPI.

Pfeifer and his collaborators will publish their findings in the March 18 issue of Physical Review Letters.

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